Input: ads7846 - power down ADC a bit later

Submit a seperate request for powering down the ADC in ads7846,
doing it after the last read request.  Otherwise some of the read
values are incorrect.

Signed-off-by: Imre Deak <imre.deak@nokia.com>
Signed-off-by: Juha Yrjola <juha.yrjola@nokia.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index 7f384a6..54d4334 100644 (file)
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -72,10 +72,11 @@ struct ads7846 {
        u16                     vref_delay_usecs;
        u16                     x_plate_ohms;
 
-       u8                      read_x, read_y, read_z1, read_z2;
+       u8                      read_x, read_y, read_z1, read_z2, pwrdown;
+       u16                     dummy;          /* for the pwrdown read */
        struct ts_event         tc;
 
-       struct spi_transfer     xfer[8];
+       struct spi_transfer     xfer[10];
        struct spi_message      msg;
 
        spinlock_t              lock;
@@ -125,7 +126,9 @@ struct ads7846 {
 #define        READ_Y  (READ_12BIT_DFR(y)  | ADS_PD10_ADC_ON)
 #define        READ_Z1 (READ_12BIT_DFR(z1) | ADS_PD10_ADC_ON)
 #define        READ_Z2 (READ_12BIT_DFR(z2) | ADS_PD10_ADC_ON)
-#define        READ_X  (READ_12BIT_DFR(x)  | ADS_PD10_PDOWN)   /* LAST */
+
+#define        READ_X  (READ_12BIT_DFR(x)  | ADS_PD10_ADC_ON)
+#define        PWRDOWN (READ_12BIT_DFR(y)  | ADS_PD10_PDOWN)   /* LAST */
 
 /* single-ended samples need to first power up reference voltage;
  * we leave both ADC and VREF powered
@@ -541,6 +544,18 @@ static int __devinit ads7846_probe(struct spi_device *spi)
        x++;
        x->rx_buf = &ts->tc.x;
        x->len = 2;
+       spi_message_add_tail(x, &ts->msg);
+
+       /* power down */
+       x++;
+       ts->pwrdown = PWRDOWN;
+       x->tx_buf = &ts->pwrdown;
+       x->len = 1;
+       spi_message_add_tail(x, &ts->msg);
+
+       x++;
+       x->rx_buf = &ts->dummy;
+       x->len = 2;
        CS_CHANGE(*x);
        spi_message_add_tail(x, &ts->msg);